Multi-speed gearbox

ABSTRACT

The multi-step reduction gear includes a drive shaft and an output shaft, having three single rod planetary gears, seven rotating shafts and six shifting elements, whose selective engagement realizes seven forward gears and one reverse gear, the drive takes place through a shaft, connected with the sun wheel of the first planetary gears. The output takes place through a shaft in connection with the annulus of the second planetary gear and the annulus of the third planetary gears. A shaft is connected with the rod of the first planetary gears; a shaft is connected with the rod of the second planetary gears and the rod of the third planetary gears; a shaft is connected with the annulus of the first planetary gear set; a shaft is connected with the sun wheel of the third planetary gears; a shaft is connected with the sun wheel of the second planetary gears.

The present invention concerns a multi-step reduction gear in planetaryconstruction, especially an automatic transmission for a motor vehiclein accordance with the preamble of claim 1.

Automatic transmissions, especially for motor vehicles, includeplanetary gear sets according to the state of the art, which are shiftedusing friction or shifting elements, such as clutches and brakes, andare usually connected with a starting element subject to a slippingaction and are optionally provided with a bridging clutch, such as ahydrodynamic torque converter or a hydraulic clutch.

A transmission of this type emerges from EP 0 434 525 A1. It basicallyincludes a drive shaft and an output shaft, which are arranged parallelto each other, and a double planetary gear set arranged concentricallyin relation to the output shaft, and five shifting elements in the formof three clutches and two brakes, whose selective blockage respectivelydetermines in pairs the various gear ratios between the drive shaft andthe output shaft. Hereby, the transmission has a control gear and twopower paths, so that six forward gears can be attained through theselective engagement in pairs of the five shifting elements.

Hereby two clutches are needed in connection with the first power pathto transmit the torque from the control gear set to two elements of thedouble planetary gear set. These are basically arranged behind thecontrol gear set in the direction of the double planetary gears in thedirection of the flow of force. A further clutch is provided inconnection with the second power path, which detachably connects thiswith a further element of the double planetary gears. Hereby theclutches are arranged in such a way that the internal disk support formsthe output.

Furthermore, a compact multi-step reduction gear in planetaryconstruction, especially for a motor vehicle, is known from thepublication U.S. Pat. No. 6,139,463, which has two planetary gears and acontrol gear set, as well as three clutches and two brakes. Two clutchesC-1 and C-3 are provided with this known multi-step reduction gear inconnection with a first power path for transmitting the torque from thecontrol gears to the two planetary gears. Here the external disk supportor the cylinder or the piston or the pressure compensation side ofclutch C-3 is connected with a first brake B-1. Moreover the internaldisk support of the third clutch C-3 is connected with the cylinder orpiston or pressure compensation side of the first clutch C-1, wherebythe internal disk support of the first clutch C-1 is arranged on theoutput side and is connected with a sun wheel of the third planetarygear set.

Moreover, a multi-step reduction gear is known from DE 199 49 507 A1 ofthe Applicant, in which two non-shiftable control gears are provided onthe drive shaft, which generate two RPMs on the output side that can, inaddition to the RPM of the drive shaft, be shifted electively to ashiftable double planetary gears acting on the output shaft throughselective closing of the shifting elements used in such a way that ineach case only one shifting element of the two shifting elements justactivated must be engaged or disengaged for shifting from one gear intothe respectively next following higher or lower gear.

Furthermore, an automatically shiftable motor vehicle transmission withthree single rod planetary gears, as well as three brakes and twoclutches for shifting from six forward gears and one reverse gear and,with a drive as well as an output shaft, is known from DE 199 12 480 A1.The automatically shiftable motor vehicle transmission is constructed insuch way that the drive shaft is directly connected with the sun wheelof the second planetary gear and that the drive shaft can be connectedwith the sun wheel of the first planetary gears through the first clutchand/or through the second clutch with the rod of the first planetarygears. In addition or as an alternative, the sun wheel of the firstplanetary gears can be connected through the first brake with thehousing of the transmission and/or the rod of the first planetary gearsthrough the second brake with the housing and/or the sun wheel of thethird planetary gears through the third brake with the housing.

The present invention is based upon the objective of proposing amulti-step reduction gear of the type stated at the beginning in whichthe construction expenditure is optimized and, moreover, the degree ofefficiency in the main driving gears is improved with respect to dragand gearing losses. Additionally, low torques should be acting on theshifting elements and planetary gears in the multi-step reduction gearof the invention and the RPMs of the shafts, shifting elements andplanetary gears should be kept as low as possible. Furthermore, thenumber of gears as well as the transmission ratio spread should beincreased.

This objective is accomplished in accordance with the invention throughthe features of patent claim 1. Further advantages and refinements willemerge from the dependent claims.

Accordingly, a multi-step reduction gear in planetary construction ofthe invention is proposed, which has a drive shaft and an output shaft,which are arranged in a housing. Furthermore, at least three single rodplanetary gears, at least seven rotating shafts, as well as at least sixshifting elements including brakes and clutches, are provided; theselective engagement of which effects various reductions between thedrive shaft and the output shaft so that preferably seven forward gearsand one reverse gear can be realized.

In accordance with the present invention, in connection with themulti-step reduction gear, it is provided that the drive is effectedthrough a shaft, which is continuously connected with the sun wheel ofthe first planetary gears and, in such a way, the output is effectedthrough a shaft, which is connected with the annulus of the secondplanetary gears and an element of the third planetary gears.Furthermore, the multi-step reduction gear of the invention providesthat a third shaft is continuously connected with the rod of the firstplanetary gears; a fourth shaft is continuously connected with the rodof the second planetary gears as well as a further element of the thirdplanetary gears; a fifth shaft is continuously connected with theannulus of the first planetary gears; a sixth shaft is continuouslyconnected with the sun wheel of the third planetary gears; a seventhshaft is continuously connected with the sun wheel of the secondplanetary gears, whereby the planetary gears are coupled by means ofshafts and shifting elements.

In the framework of a preferred embodiment, the output shaft isconnected with the annulus of the second planetary gears and the annulusof the third planetary gears whereby, in this case, the fourth shaft isconnected with the rod of the second and the rod of the third planetarygears and the first planetary gears and the second planetary gears areconstructed as negative planetary gears and the third planetary gears aspositive planetary gears.

In accordance with a further embodiment, the output shaft is connectedwith the annulus of the second planetary gears and the rod of the thirdplanetary gears whereby, in this case, the fourth shaft is connectedwith the annulus of the third planetary gears and the rod of thesecondary planetary gears. Hereby the three planetary gears areconstructed as negative planetary gears.

Several suitable reductions, as well as a considerable increase of theoverall spread of the multi-step reduction gear, are the result of thisconfiguration of the multi-step reduction gear in accordance with theinvention, owing to which an improvement in driving comfort, and asignificant reduction in consumption are brought about.

The multi-step reduction gear of the invention is suitable for any motorvehicle, especially for passenger cars and for commercial motorvehicles, such as for example, trucks, busses, construction vehicle,rail vehicles, caterpillar vehicles and the like.

In addition, the construction expenditure is significantly reduced withthe multi-step reduction gear of the invention because of the low numberof shifting elements, preferably four clutches and two brakes. With themulti-step reduction gear of the invention, it is advantageouslypossible to conduct a start with a hydrodynamic converter, an externalstarting clutch or also with other suitable external starting elements.It is also conceivable to enable a starting procedure with a startingelement incorporated into the transmission. Preferably a shiftingelement, which is activated in first gear and in reverse gears, issuitable.

In addition, the multi-step reduction gear of the invention results in agood degree of efficiency in the main driving gears with respect to dragand gearing losses.

Moreover, low torques are present in the shifting elements and theplanetary gears of the multi-step reduction gear, owing to which, thewear and tear on the multi-step reduction gear, is advantageouslyreduced. Furthermore, due to the low torques, a correspondingly smalldimensioning is made possible, owing to which the space required and thecorresponding costs, can be reduced. In addition, low RPMs are alsopresent in the shafts, shifting elements and planetary gears.

Furthermore, the transmission of the invention is designed in such a waythat an adaptability to different power train configurations in thedirection of the force flow, as well as with respect to space, is madepossible.

The invention will be explained in greater detail below by way ofexample on the basis of the drawings, wherein:

FIG. 1 represents a schematic view of a preferred embodiment of amulti-step reduction gear of the invention;

FIG. 2 represents a schematic view of an additional preferred embodimentof a multi-step reduction gear of the invention and;

FIG. 3 represents a shifting diagram for the multi-step reduction gearof the invention in accordance with FIG. 1 and FIG. 2.

FIG. 1 shows the multi-step reduction gear of the invention with a driveshaft 1 (An), and an output shaft 2 (Ab), which are arranged in ahousing G. Three single rod planetary gears P1, P2, P3 are provided.Here the first planetary gears P1 and the second planetary gears P2 areconstructed as negative planetary gears. The third planetary gears P3are constructed as positive planetary gears in accordance with theinvention. It is also possible that the second planetary gears P2 andthe third planetary gears P3 are combined as Ravigneaux planetary gearswith common rod and common annulus.

As is apparent from FIGS. 1 and 2, only six switching elements, namely,two brakes 03, 04, and four clutches 14, 16, 37 and 57 are provided.

A selective shifting of seven forward gears and one reverse gear can berealized by means of the shifting elements. The multi-step reductiongear of the invention accordingly consists of a total of seven rotatingshafts, namely, the shafts 1, 2, 3, 4, 5, 6, and 7.

In accordance with the invention, it is provided with the multi-stepreduction gear, in accordance with FIG. 1, that the drive takes placethrough shaft 1, which is continuously connected with the sun wheel ofthe first planetary gears P1. The output takes place through shaft 2,which is connected with the annulus of the second planetary gears P2 andthe annulus of the third planetary gears P3. Furthermore, shaft 3 iscontinuously connected with the rod of the first planetary gears andshaft 4 is continuously connected with the rod of the second planetarygears P2 and the rod of the third planetary gears P3. In addition, shaft5 is continuously connected with the annulus of the first planetarygears P1. The further rotating shaft 6 is continuously connected withthe sun wheel of the third planetary gears P3 and the shaft 7 with thesun wheel of the second planetary gears P2 in accordance with theinvention.

With the multi-step reduction gear of the invention, the shaft 3 can becoupled onto the housing G through the brake 03, and the shaft 4 throughthe brake 04. The clutch 14 connects shaft 1 and shaft 6 detachably withone another. Shaft 1 and shaft 6 are detachably connected with eachother through clutch 16. Furthermore, clutch 37 detachably connectsshafts 3 and 7, and clutch 57 detachably connects shafts 5 and 7 witheach other.

A further embodiment of the multi-step reduction gear of the inventionis shown in FIG. 2. Hereby, the planetary gears P1, P2 and P3 areconstructed as negative planetary gears. A further difference from theembodiment of FIG. 1 consists in that the output shaft 2 is connectedwith the annulus of the second planetary gears P2, and the rod of thethird planetary gears P3, and in that shaft 4 is continuously connectedwith the rod of the second planetary gears P2 and the annulus of thethird planetary gears P3.

A shifting diagram of the multi-step reduction gear of the invention inaccordance with FIGS. 1 and 2 is represented in FIG. 3. Respectivereductions i of the individual gear stages, and stage progressions φ tobe determined on the basis of them, can be inferred by way of example.Furthermore, it can be inferred from the shifting diagram that doubleshifts can be avoided with sequential modes of shifting, since twoadjacent gear steps respectively use two shifting elements in common.

The brake 03 is continuously closed for the seven forwards gear. Inaddition, brake 04 and clutch 57 are activated for the first gear; forsecond gear, brake 04 and clutch 16; for the third gear, clutch 16 andclutch 57; for the fourth gear, clutches 16 and 37; for the fifth gear,clutches 14 and 16; for the sixth gear, clutches 14 and 37; and for theseventh gear, clutches 14 and 57. In reverse gear R, brake 04 andclutches 37 and 57 are activated as shift elements.

In accordance with the invention, it is possible to provide additionalfree wheelings at each suitable position of the multi-step reductiongear, for example, to be connected between a shaft and the housing orabout two shafts if need be.

Moreover, it is possible through the mode of construction of theinvention to arrange the drive and output on the same side of thetransmission or the housing preferably for transverse, frontal,longitudinal, back longitudinal or all wheel arrangements. Moreover, anaxle differential and a distributor differential can be arranged on thedrive side, or on the output side.

The drive shaft 2 can be separated by a clutch element from a drivemotor, as needed, within the framework of an advantageous furtherdevelopment, whereby a hydrodynamic converter, a hydraulic clutch, a drystarting clutch, a wet starting clutch, a magnetic powder clutch or acentrifugal force clutch can be used. It is also possible to arrange astarting element of this type behind the transmission in the flow offorce direction whereby, in this case, the drive shaft 1 is continuouslyconnected with the crankshaft of the motor. The start up can take placeusing a shifting element of the transmission. Preferably the brake 04,which is activated in the first forward gear, as well as in the firstreverse gear, can be used.

The multi-step reduction gear of the invention enables the arrangementof a torsion vibration damper between motor and transmission.

A wear-free brake, such as a hydraulic or electric retarder or the like,can be arranged on any shaft, preferably on the drive shaft 1 or theoutput shaft 2, which is especially of significance for use incommercial motor vehicles within the framework of a further, notrepresented embodiment. Furthermore, an auxiliary output can be providedpreferably on the drive shaft 1 or the output shaft 2 for drivingadditional units on each shaft.

The shifting elements used can be constructed as load-shifting clutchesor brakes. In particular, force-locking clutches or brakes such as diskclutches, strap brakes and/or cone clutches, can be used. Furthermore,form-locking brakes and/or clutches, such as synchronizations or clawclutches, can be used as shifting elements.

A further advantage of the multi-step reduction gear presented hereconsists in that an electric machine can be installed on each shaft asgenerator and/or as additional drive machine.

The functional features of the claims can be constructionally built inmore different types of ways. These constructional developmentpossibilities are not being explicitly described for the sake ofsimplicity. Obviously, each constructional development of the invention,nonetheless, falls under the scope of protection of the claims,especially any spatial arrangement of the planetary gears or theshifting elements in themselves or toward one another and to the extentto which they are technically appropriate.

REFERENCE NUMERALS

-   1 shaft-   2 shaft-   3 shaft-   4 shaft-   5 shaft-   6 shaft-   7 shaft-   03 brake-   04 brake-   14 clutch-   16 clutch-   37 clutch-   57 clutch-   P1 planetary gears-   P2 planetary gears-   P3 planetary gears-   An drive-   Ab output-   i reduction-   φ step progression-   G housing

1-21. (canceled)
 22. A multi-step reduction gear in planetaryconstruction, especially an automatic transmission for a motor vehicle,including a drive shaft (1) and an output shaft (2), which are arrangedin a housing (G), first, second and third single rod planetary gears(P1, P2, P3), at least the first, the second, a third, a fourth, afifth, a sixth and a seventh rotating shafts (1, 2, 3, 4, 5, 6, 7), aswell as at least six shifting elements (03, 04, 14, 16, 37, 57),including first and second brakes and first second, third, and fourthclutches, whose selective engagement brings about different reductionratios between the drive shaft (1) and the output shaft (2), so thatseven forward gears and one reverse gear can be realized, wherein drivetakes place through the drive shaft (1), which is continuously connectedwith a sun wheel of the first planetary gears (P1), output takes placethrough the output shaft (2), which is continuously in connection withan annulus of the second planetary gear set (P2) and an element of thethird planetary gears (P3), the third shaft (3) is continuouslyconnected with a rod of the first planetary gears (P1), the fourth shaft(4) is continuously connected with a rod of the second planetary gears(P2), and a further element of the third planetary gears (P3), the fifthshaft (5) is continuously connected with an annulus of the firstplanetary gear set (P1), the sixth shaft (6) is continuously connectedwith a sun wheel of the third planetary gears (P3), the seventh shaft(7) is continuously connected with a sun wheel of the second planetarygears (P2), whereby the third shaft (3) can be coupled to the housing(G) through the first brake (03), the fourth shaft (4) can be coupled tothe housing (G) through the second brake (04), the first clutch (14)detachably connects the first drive shaft (1) and the fourth shaft (4)with each other, the second clutch (16) detachably connects the driveshaft (1) and the sixth shaft (6) with each other, the third clutch (37)detachably connects the third shaft (3) and the seventh shaft (7) witheach other, and whereby the fourth clutch (57) detachably connects thefifth shaft (5) and the seventh shaft (7) with each other.
 23. Themulti-step reduction gear according to claim 22, wherein the secondshaft (2) is connected with the annulus of the second planetary gears(P2) and an annulus of the third planetary gears (P3), and wherein thefourth shaft (4) is continuously in connection with the rod of thesecond planetary gears (P2) and a rod of the third planetary gears (P3),whereby the first planetary gears (P1) and the second planetary gears(P2) are constructed as negative planetary gears, and the thirdplanetary gears (P3) is constructed as positive planetary gears.
 24. Themulti-step reduction gear according to claim 23, wherein the secondplanetary gears (P2) and the third planetary gears (P3) are combined asRavigneaux planetary gears with a common rod and a common annulus. 25.The multi-step reduction gear according to claim 22, wherein the outputshaft (2) is connected with the annulus of the second planetary gears(P2) and the rod of the third planetary gears (P3), and the fourth shaft(4) is continuously connected with the rod of the second planetary gears(P2) and a hollow shaft of the third planetary gears (P3), whereby thefirst, second and third planetary gears (P1, P2, P3) are constructed asnegative planetary gears.
 26. The multi-step reduction gear according toclaim 22, wherein additional free wheelings can be used on any suitableposition.
 27. The multi-step reduction gear according to claim 26,wherein the free wheelings are provided between the drive, the first,second, third, fourth, fifth, sixth and seventh output shafts (1, 2, 3,4, 5, 6, 7) and the housing (G).
 28. The multi-step reduction gearaccording to claim 22, wherein a drive and an output are provided on asame side of the housing.
 29. The multi-step reduction gear according toclaim 22, wherein one or more of an axle and a distributor differentialis arranged on one of a drive side or an output side.
 30. The multi-stepreduction gear according to claim 22, wherein the drive shaft (1) isseparable from a drive motor through a clutch element.
 31. Themulti-step reduction gear according to claim 30, wherein the clutchelement is one of a hydrodynamic converter, a hydraulic clutch, a drystarting clutch, a wet starting clutch, a magnetic powder clutch, or acentrifugal clutch.
 32. The multi-step reduction gear according to claim31, wherein an external starting element can be arranged behind thetransmission in a force of flow dimension, whereby the drive shaft (1)is in a fixed connection with a crankshaft of the motor.
 33. Themulti-step reduction gear according to claim 22, wherein starting takesplace using a shifting element of the transmission, whereby the driveshaft (1) is continuously connected with a crankshaft of the motor. 34.The multi-step reduction gear according to claim 33, wherein the fourthclutch (57) or the second brake (04) can be used as a shifting element.35. The multi-step reduction gear according to claim 22, wherein atorsion vibration damper can be arranged between a motor and thetransmission.
 36. The multi-step reduction gear according to claim 22,wherein a wear-free brake can be arranged on each shaft.
 37. Themulti-step reduction gear according to claim 22, wherein an auxiliaryoutput can be arranged on each shaft for driving additional units. 38.The multi-step reduction gear according to claim 37, wherein theauxiliary output can be arranged on one of the drive shaft (1) or theoutput shaft (2).
 39. The multi-step reduction gear according to claim22, wherein the shifting elements are constructed as load-shiftingclutches or brakes.
 40. The multi-step reduction gear according to claim39, wherein one or more of disk clutches, strap brakes and cone clutchescan be used as the shifting elements.
 41. The multi-step reduction gearaccording to claim 22, wherein one or more of form-locking brakes andclutches are provided as the shifting elements.
 42. The multi-stepreduction gear according to claim 22, wherein an electrical machine canbe installed on each shaft as one or more of a generator and anadditional drive machine.